1. Field of the Invention
This invention relates to windshield wipers and more particularly to the connection between a wiper arm and a wiper blade for holding the blade in a plane substantially perpendicular to the underlying surface of the windshield as the wiper arm traverses an arc across the windshield.
2. Background of the Invention
Wrap around windshields have presented a serious challenge to the windshield wiper industry. Normally, the main portion of the windshield is substantially flat or only moderately curved and falls away relatively sharply at the outboard portions thereof. It has been recognized for some time that most wrap around windshields have straight or only moderately curved components in a direction along a line perpendicular to the lower belt line of the windshield, but have curvatures in a plane parallel to the belt line of the windshield that varies from moderately curved to sharply curved. Conventional wiper blades that are connected to a wiper arm so that they function along a line generally parallel to the wiper arm are not able to completely conform to the sharply curved side portions of the windshield so that the outboard sides of the windshield remain unwiped. To overcome this problem, wiper arms having a parallelogram linkage were developed whereby the wiper blade was held substantially perpendicular to the lower belt line as it is moved across the windshield. In this way, the wiper blade flexes along its length relatively little as it wipes the windshield. However, at the outboard ends of the wipe pattern, the windshield curves away from the wiper blade so that the blade is not perpendicular to the surface of the windshield, resulting in less than a satisfactory wipe. Attempts have been made to provide a mechanism for changing the attitude of the wiper blade so as to maintain the blade perpendicular to the surface of the windshield being wiped even at the outboard reaches of the windshield.
One such attempt is disclosed in U.S. Pat. No. 3,292,200 to Scinta. In Scinta, a segmented wiper arm is provided which allows pivoting of the blade-carrying section of the arm about an axis that is transverse to the arm length. The blade-carrying section is spring biased to urge the wiper blade about the pivot conformingly against the windshield. This construction does not lend itself to incorporation into a pantograph type assembly, wherein the orientation of the wiper blade is maintained constant. Further, the two-diemensional pivoting can conform the blade to only a limited number of windshield configurations.
Another proposed solution is disclosed in U.S. Pat. No. 3,180,757 to Wise. In Wise, a component carried by a housing on the wiper blade has an internal groove for accepting an entering part on a wiper arm, which part is curved to correspond to the curvature of the internal groove in the housing. The entering part and groove cooperate to effect multi-dimensional adjustment between the wiper arm and blade to hold the blade in a plane perpendicular to the windshield. Because of the relative movement required between the entry member and the blade component, the connection might be prone to jamming, causing the wiper blade to be ineffectual on either the curved or flat portions of the windshield.
The present invention is specifically directed to overcoming one or more of the above enumerated deficiencies known in the prior art.